The objectives of this project are: (1) to identify, adapt and pretest methods of measuring the bacterial and chemical composition of dental plaque and saliva; and, (2) to conduct short-term clinical studies of agents which might be capable of restricting dental plaque and caries. The present studies investigated the effects of DCPD pretreatments used weekly as a tray applied gel and SnF2 used twice daily as an oral rinse on dental plaque and gingivitis and fluoride uptake by the outer enamel. Stannous fluoride treatments restriced plaque extent and the pH drop in plaque following a sucrose rinse. DCPD pretreatments augmented fluoride uptake by the enamel without interfering with the antiplaque effects of the SnF2 treatments.